1. Technical Field
This invention relates to an anvil assembly for a surgical fastener applying instrument. More particularly, this invention relates to a pivotable anvil assembly for a circular anastomosis surgical stapling instrument.
2. Background of Related Art
Various types of surgical fastener applying instruments are known for the application of surgical fasteners to tissue. A common type of surgical fastener is a surgical staple. Surgical stapling instruments typically have a mechanism for firing a plurality of staples from a staple holding cartridge and an anvil disposed opposite the staple cartridge against which the staples are formed. Such instruments include, for example, linear staplers, which typically apply one or more parallel rows of staples, and circular staplers, which typically apply one or more concentric/circular rows of staples. In use, the surgeon will place tissue between the staple cartridge and anvil and, by firing the instrument, cause the staples to become clenched to the tissue.
Circular staplers are known and have been successfully used in surgical procedures for many years. Commercially available instruments include the CEEA.RTM. circular stapler, manufactured by United States Surgical Corporation, Norwalk, Conn., and the ILS.RTM. circular stapler, manufactured by Ethicon, Inc., Blue Ash, Ohio. Various embodiments of circular staplers have been disclosed in commonly assigned U.S. Pat. Nos. 4,576,167, 4,603,693, 5,005,749, and 5,119,983. These instruments are typically indicated for use in gastric and esophageal surgery wherein tubular organs are joined to other anatomical structures.
In one common procedure, known as end-to-end anastomosis, a portion of the intestinal tract is removed (i.e., due to the presence of disease such as cancer) and the remaining ends are rejoined by using a circular stapler. To join the tubular structures, one end of intestine is secured about an anvil and the other end of intestine is held in place adjacent a staple cartridge. Preferably, the anvil has a shaft that is removably connected to the instrument. Once the anvil shaft is secured to the instrument, the anvil is drawn into close approximation to the stapling cartridge. The instrument is then fired to cause the staples to pass through tissue of both organs and become formed against the anvil. During the firing step, a circular knife is advanced to cut tissue inside the staple line, thereby establishing a passage between the organs. After firing, the instrument is typically removed by withdrawing the anvil through the staple line, after which the surgeon will carefully inspect the surgical site to ensure a proper anastomosis (joining) has been achieved.
During withdrawal of the anvil, there can be a noticeable resistance as the anvil passes by the staple line. Since the staples have been freshly placed and tissue freshly cut, minimal manipulation of the surgical sight is desired. A proposed solution to reduce removal force is found in U.S. Pat. No. 4,505,272, issued in 1985 to Utyamyshev, et at. The '272 patent discloses an anvil which breaks into four pieces after firing, and, therefore, is more easily pulled through the stapled anastomosis. Unfortunately, the construction of Utyamyshev's anvil is quite complicated and would be expensive to manufacture. Ethicon, Inc., in its ILS.RTM. circular stapler, has chosen to have the knife cut relatively close to the staple line, thereby providing a larger opening for the anvil. A disadvantage of this design, however, is that the surgical site has less tissue in the stapled area and can be more prone to leakage or rupture.
A more economical and efficacious approach to decrease resistance upon anvil removal was developed by U.S. Surgical, and is disclosed in European Patent Application No. 570,915 A2. This application discloses an anvil that pivots relative to a portion of the anvil shaft. Pivoting allows the anvil to move to a position wherein a smaller surface area of the anvil passes through the anastomotic sight, as compared to the surface area with no pivoting. While this pivoting anvil is useful, it could be improved by providing structure that permits control over the pivoting movement of the anvil relative to the shaft.
Therefore, there is a need to provide a circular stapling instrument having an anvil that is easily removed from the surgical site. This need should be satisfied without compromising the safety of the patient and, particularly in this era of "Health Care Reform", this need should be satisfied in a cost effective manner.
When performing a circular anastomosis, proper alignment of the knife and complete severance of all structures in the path of the knife blade is key to successful operation of the instrument. The difficulty of this cutting step can be dependent on the technique used by the surgeon. In so called "triple stapling" procedures, for example, the intestine ends to be joined are each initially closed by one or more lines of staples. When joining is performed with a circular stapler, one or more of these lines of staples can become disposed between the anvil and staple cartridge. In this event, during the cutting step, the knife blade can come into contact with both tissue and one or more staples. To facilitate cutting of tissue, it is well known in the art to provide plastic or other semi-rigid ring members in the path of the knife blade. See, for example, U.S. Pat. Nos. 4,289,133, 4,304,236 and 5,119,983. While these structures are effective in aiding the knife to cut tissue, staples can remain uncut and deformed after firing. Such uncut staples are undesirable.
Therefore, a need exists for circular staplers wherein the cutting knife can sever both tissue and staples during use. In addition, there is a need to ensure proper alignment of the knife with that which it is designed to contact in order to sever the tissue and staples.